An Open Source IMS Initiative for the Research Community

Transcription

1 The Open Source IMS Core An Open Source IMS Initiative for the Research Community 1

2 Motivation for an Open Source IMS Core IMS is in trial phases with telco and cable operators worldwide R&D efforts for NGNs are gaining support While there are already many Open Source projects established in the plain VoIP area for SIP clients SIP proxies SIP stacks SIP (testing) tools around the standard, there are currently practically no Open Source projects with specific focus on the IMS FOKUS is aiming to fill this void 2

3 Open IMS Core Components Access Network Home Network Cx SIP-to-IMS Gateway G m M w Interrogating-CSCF Home Subscriber Server G m Mw C x Sh G m Proxy-CSCF M w ISC Serving-CSCF 3

4 Call Session Control Functions CSCF = SIP proxy to route and process the SIP signaling Proxy-CSCF outbound proxy for User Endpoints entry point in the IMS network keep local registrar and firewall the core network add important network/charging/etc information to the messages bridge between access network (visited network) and user s home network Interrogating-CSCF entry point in the Home Network originating/terminating party assigned Serving-CSCF retrieval stateless forwarding of messages I-CSCF Serving-CSCF local registrar for served users authenticate the users subscription server for registration status events S-CSCF evaluate Initial Filter Criteria and route messages accordingly to Application Servers for service processing 4

5 HSS & SIP2IMS Gateway Home Subscriber Server evolution of a Home Location Register to the all-ip core network stores user profile, provisioning data keeps registration status keeps location information HSS SIP2IMS Gateway allows transformation of IETF SIP messages to IMS conformant messages Translates MD5 authentication to IMS AKA authentication 5

6 Elements around the Open IMS Core Functionalitly of the Open IMS Core can be verified with additonal components IMS UE must be capable of performing IMS AKA registration IMS specific SIP behaviour e.g. subscription to own registration event SIP client uses IETF SIP protocols without IMS extensions (e.g. Kphone, eyebeam) attaches to IMS Core via SIP2IMS Gateway Application Servers tested Service platforms for the Open IMS Playground SIPSEE (SIP AS) Open Coummincation Server (Parlay Gateway) Open Communication Server X (Parlay X Gateway) SIP Client AS 6

7 CSCF Implementation SER = SIP Express Router a high-performance, carrier-grade, open source, configurable SIP server written in C ported to Linux and Solaris throughput thousands of CPS (calls per second) on a dual-cpu PC (capacity needed to cover San Francisco s Bay Area) and hundreds of CPS on a Compaq ipaq support for both IPv4 and IPv6 small footprint size: 300k core, all common modules around 600k extended flexibility through script-like configuration Each CSCF is implemented as a SER module Script usage example: Excerpt from the Proxy-CSCF configuration file steps are applied in order in the routing script if (method== INVITE method== SUBSCRIBE method== MESSAGE ) { if (!P_is_registered( open-ims.org )){ sl_send_reply( 403, Forbidden You must register first ); break; } P_add_P_Charging_Vector(); P_add_P_Visited_Network_ID( Visited Network Number 1 ); } 7

8 HSS Implementation Prototypical implementation of a Home Subscriber Server Realized in Java Based upon Open Source Software (e.g. MySQL, Tomcat) Pure IP-based interfaces Blends out all HLR related interfaces Diameter reference points supported so far Cx for IMS registration processes (AKA with vector generation using MILENAGE) Sh for IMS application platform support Compliant with 3GPP Rel. 6 specifications Web-based management interface GMSC Mobility Management User Security Support Application Service Support Service Authorization Support MSC VLR BSF SGSN GGSN WLAN SIP AS OSA SCS IM SSF CSCF CS domain PS domain IMS domain 8

9 Specification Guidelines for the Open Source IMS Core IETF RFCs (selection) SIP: Session Initiation Protocol RFC 3261 Hypertext Transfer Protocol (HTTP) Digest Authentication Using Authentication and Key Agreement (AKA) - RFC 3310 SIP Private Header Extensions - RFC3455 Diameter Base Protocol RFC 3588 SIP Event Package for Registration - RFC3680 3GPP IMS Release 6 Specifications (selection) TS IMS Stage 2 (Rel.6) TS IP Multimedia Call Control Protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage3 (Rel.6) TS Cx and Dx Interfaces, Signalling flows and message contents (Rel.6) TS G Security; Security architecture (Rel. 6) TS Access security for IP-based services (Rel.6) 9

10 The Open Source IMS Core A version of the Open IMS Core is currently being developed and was already successfully tested with commercial IMS products. It provides first time implementations of core IMS components Call Session Control Functions Home Subscriber Server offers an Open Source IMS platform to make use of the ISC interface can act as a tool for IMS services proof-of-concept allows to test alpha/beta versions of commercial IMS products does not intend to compete with carrier grade developments but wants to create an Open IMS community and to accelerates IMS adoption release of the CSCFs scheduled for end of 2006 via the BerliOS ( platform For further information please contact {weik,vingarzan}@fokus.fraunhofer.de 10